Electromagnetic apparatus



5. w. BARNES ELECTROMAGNETIC APPARATUS June 4, '1957 Filed April 2, 1946 IN VEN TOR.

7 6711 226 211 .fiarzzes United. States Patent ELECTROMAGNETIC APPARATUS Sidney W. Barnes, Rochester, N. Y., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commis' sion Application April 2, 1946, Serial No. 658,946

4 Claims. (Cl. 250-413) The present invention relates to apparatus for separating charged particles, such as ions, by utilizing the magnetic mass spectrum thereof.

One form of apparatus which has been used for this purpose comprises the combination of a partially evacuated closed vessel and a magnetic field of such strength as to constrain uniform velocity ions projected within the vessel to motion on circles having radii which are a predetermined fixed function of the momentum of the ions. By such means it is known that ions having "a common origin and traveling different paths of equal curvature will, due to geometrical focusing action, substantially pass through a common region after 180 of travel.

In order for apparatus of the above type to have practical utility as a means for making isotopes available in quantity, it is necessary to collect separately the ions differing in mass i. e., the different isotopes, so that they may be recovered to provide materials having greater proportions of isotopes than occur in nature. While the apparatus of the present invention is not limited to the separation of the isotopes of any one element, it must of necessity be specially adapted for the masses involved and in order for its principles to be clearly understood the invention will be described as employed in the separation of the uranium isotopes having atomic weights 235 and 238. The other isotope, having an atomic weight of 234, comprises such a small proportion of natural uranium that its existence will be ignored in the following description. It will be understood however that the 234 isotope is present and acquires importance when most of the 238 isotope has been removed.

For the reception and retention of electromagnetically separated isotopes, it is generally necessary to provide closely adjacent pockets and for several reasons, including longer life, it is desirable to have the wall separating the two pockets at 0 i. e., tangent to the curvature of the dividing line between the two isotopes at the point of collection. However, such an arrangement of the separating wall makes it certain that opposite sides of the wall will receive dififerent isotopes, and accordingly, the deionizing cur-rents to the two pockets are riot'true readings of the isotopes being received i. e., neither isotope is electrically resolved. It thus is desirable to provide an arrangement with which the operator can determine if the desired state of reception exists, and if not existing, can then make needed adjustments in the apparatus.

A primary object of the present invention is the provision of simple means with which the operator may at will obtain information about the quality of reception in the apparatus.

Another object of the invention is the provision of an electrode movable into the optimum receiving position of one of the isotopes for indicating whether or not such isotope is being received as desired.

Another object of the invention is the provision of a Patented June 4, 1957 novel motor means for efiecting the movement of such movable electrode.

Other objects and advantages of the invention will become apparent from the following description when read in connection with the accompanying drawing, and its novel features will be pointed out in the appended claims.

In the drawing:

Fig. 1 is a conventionalized showing in section of an apparatus in which the invention may be incorporated;

Fig. 2 is a view in perspective of the receiver box in Fig. 1 showing the movable electrode and its magnetic operating means; and

Fig. 3 is a fragmentary view in'section showing the magnetic means and its heating coil.

The arrangements shown in the drawing are in the main largely diagrammatic and consist of only those features necessary to a complete understanding of the invention. The various supporting structures and auxiliary equipment may take any suitable form known to those skilled in the art and constitute no part of the present invention. Accordingly such structure and equipment have not been shown since it would serve only to obscure rather than disclose the invention.

Referring to Fig. 1, there is shown a closed vessel 10 positioned in a strong magnetic field provided by a magnet one pole piece 11 of which is shown. The vessel 10 provides a space within which electromagnetic separation of ions may take place and is preferably highly evacuated although the presence of a small amount of gas is desirable under some circumstances to avoid so-called space charge effects.

Within the closed vessel 10 and also within the region of influence of the magnetic field produced by the pole piece 11, there is provided :a source 12 of ions of a material, the isotopes of which it is desired to separate, and which in conjunction with an accelerating electrode 13 serves to project in a direction normal to the magnetic field a stream or beam of high velocity ions. The accelerating electrode 13 is made negative with respect to the ion source 12 from any suitable direct current supply which preferably is adjustable. As is well known, these accelerated ions in traversing the magnetic field will be forced to follow circular orb-its which results in the formation of the magnetic mass spectrum of the ions after approximately of travel from the accelerating electrode 13. If, as is here assumed, the ions consist primarily of the two isotopes of uranium, the 238 ions will follow orbits having the curvature indicated by a path Q. Similarly 235 ions will describe orbits of stronger curvature indicated by a path R.

For the reception of the ion beams Q and R a receiver 14 having 21 0 wall 15 dividing it into two pockets is positioned to receive the Q and R beams at the point of greatest separation i. e., after 180 of travel, and for convenience these two pockets will be referred to as the Q and R pockets, respectively. Face plates 16 and 17 serve to define restricted openings to the Q and R pocketsof a shape to fit the foci of the Q and R beams. With this arrangement it is obvious that the faces of the wall 15 will be bombarded by portions of both the Q and R beams and that the deionizing currents to the Q and R pockets are not electrically resolved. Even so, it is de sirable to provide a meter 18 to measure the combined deionizing currents and thus furnish the operator with an indication of the efficiency of the ion source 12.

For efficient separation of the two isotopes the positions of the Q and R beams are quite critical and it is necessary for the operator to know accurately where these beams are striking in order properly to adjust them as by adjusting the accelerating voltage between the ion source 12 and the accelerating electrode 13. In accordance with the invention an electrode 19 movable at the will of the operator into position over the opening to the Q pocket is connected to a suitable meter 29 so that whenthe deionizing current to theelectrode 19 is a maximum the operator will know that the Q pocket will receive its intended isotope and by geometry knows that the other isotope is entering the R pocket. When this desired condition exists the electrode 19 is returned to the position shown in Fig. 1. From time to time the operator will move the electrode 19 to its monitoring position as indicated in broken lines in order to check the state of reception.

Since the apparatus must function in a strong magnetic field and under very low pressure, the moving of the monitoring electrode 19 presents a problem. In accordance'with the invention this problem is solved by biasing the electrode 19 to one position and utilizing the magnetic field of the apparatus to move it to its other position. As shown in Fig. 2 the monitoring electrode 19 is mounted on the receiver box 14 by two parallel links 21 and 22 preferably of insulating material although the electrode 19 may be electrically isolated in any other suitable manner. The link 21 is pivoted at 23 on the face plate 17 and the link 22 is pivoted at 24 on an angle extension 25 secured to the end wall of the receiver box 14. The angle extension 25 is provided with a boss or raised portion 26 to form a stop for the link 22 when the electrode 19 is in non-monitoring position as shown in broken lines. An angle member 27 of insulating material is mounted on the end wall of the receiver box 14 in position to act as a stop member for the electrode 19 when in monitoring position as shown. The electrode 19 is biased to monitoring position in any suitable way as by a coiled spring 28 having one end secured to the link 22 and the other end anchored to the stop member 27. The link 22 extends beyond its fixed pivot 24 and has secured to its outer end a body 29 of magnetic material which, due to the constantly energized magnetic field, moves the link 22 and hence the electrode 19 to the non-monitoring position shown in broken lines in Fig. 2. In order to permit the spring 28 to move the electrode 19 to monitoring position, the body 29 comprises a thin shell of magnetic material surrounding a coil 30 adapted to be heated at the will of the operator from any suitable source of current such as a battery 31 through a push-button switch 32. This arrangement is shown in detail in Fig. 3.

With the system above described the shell 29 when cold, or at least below its curie point, responds to the force of the magnetic field to move the electrode 19 to non-monitoring position and to hold it there against the biasing force of the spring 28. When the operator wants to monitor reception for any reason he presses switch 32 to energize the coil 30 which then heats the body or shell 29 above the curie point of the particular material employed. The shell 29 thus becomes paramagnetic and is no longer substantially influenced by the magnetic field, thereby enabling the spring 28 to move the electrode to monitoring position. When monitoring has been completed the switch 32 is opened, andthe coil 30 and the shell 29 cool below the curie point, at which time the shell 29 is again attracted by the magnetic field to move the electrode to non-monitoring position.

The material for the shell 29 may be iron or any of the many alloys known as curie point metal as long as the curie point temperature is safely above the ambient temperature within the portion of the apparatus in which the shell 29 is to be located.

It will be evident from the above description that the invention provides 1 a simple and effective arrangement whereby monitoring may be done at will and without moving parts extending through the walls of the vessel 10.

While for the purpose of illustrating the invention a specific embodiment has been described, it is to be understood that other embodiments are contemplated as coming within the invention the scope of which is pointed out in the appended claims.

I claim:

1. In an electromagnetic isotope separating apparatus in which the isotopes are received and collected in closely adjacent pockets the deionizing currents to which are not electrically resolved, a conducting member adapted to occupy either of two positions in one of which it substantially shields the entrance to one of the pockets and in the other position does not interfere with the reception of the isotopes, said member being electrically insulated from said pockets, means for indicating the deionizing current to said member, and means for moving said member from either position to the other.

2. In isotope separating apparatus in which separation takes place at low pressure and in a strong magnetic field, a part mounted within the apparatus for movement between two positions, means biasing the part to one position, a thermo-magnetic body for overpowering the biasing means when aifected by the magnetic field, a heater element fixedly at-tach'ed to said body so as to move therewith and adapted when energized to heat said body to the curie point, and means for energizing the heater element at will.

3. In isotope separating apparatus including a receiver box inside a partially evacuated vessel positioned in a strong magnetic field, an entrance slot in the receiver box intended for the reception of ions of a single isotope, a conducting member mounted within the vessel for movement from and to a position in front of the entrance slot, said member being electrically insulated from said receiver box and having substantially the same shape and size as said slot, whereby when in said position said member intercepts the ions which would otherwise enter said slot,,means for biasing said member in said position, a body of curie point material adapted under the force of the magnetic field to move and hold said member away from said, position, an electric heating element adapted when energized to render the curie point material body paramagnetic, means exteriorly of the vessel for controlling the energizing of said heating element, and meter means for indicating the rate ions are intercepted by said member, whereby an operator may check at will the rate ions are received through the entrance slot in question.

4. A device for producing mechanical movement within apparatus functioning in a constantly energized magnetic field comprising a pivoted member having at a free end an electric heating coil surrounded by a shell of magnetic material, whereby the force exerted by the magnetic field on the shell moves the member about its pivot to a predetermined position, resilient means tending to hold the member in another predetermined position but yieldable to the superior force on the shell, and means for energizing said heating coil to render the shell paramagnetic, whereby the resilient means moves the member to said other predetermined position.

References Cited in the file of this patent UNITED STATES PATENTS 738,107 Saveur et a1. Dec. 29, 1903 1,779,604 Knerr Oct. 28, 1930 2,318,666 Bruce May 11, 1943 2,318,720 Sewell May 11, 1943 

2. IN ISOTOPE SEPARATING APPARATUS IN WHICH SEPARATION TAKES PLACE AT LOW PRESSURR AND IN A STRONG MAGNETIC FIELD, A PART MOUNTED WITHIN THE APPARATUS FOR MOVEMENT BETWEEN TWO POSITIONS, MEANSD BIASING THE PART TO ONE POSITION, A THERMO-MAGNETIC BODY FOR OVERPOWERING THE BIASING MEANS WHEN AFFECTED BY THE MAGNETIC FIELD, A HEATER ELEMENT FIXEDLY ATTACTED TO SAID BODY SO AS TO MOVE THEREWITH AND ADAPTED WHEN ENERGIZED TO HEAT SAID BODY TO 